Certain mechanical systems include a driving shaft and a driven shaft. The driving shaft may be part of, for example, a gear box and the driven shaft may be part of an accessory of receives rotational energy from the driving shaft. The two shafts may be joined by a spline joint.
A spline joint may include splines (ridges or teeth) on a drive shaft that mesh with grooves in a mating piece and transfer torque to it, maintaining the angular correspondence between them. For instance, the driving shaft may include a male spline on the shaft that matches the female spline on the driven shaft or vice versa.
In operation, the spline joint may need lubrication from time to time.